How to display an image in frontend with link for full size?

Hi,

To display the images in thumbnail with links to the full-size, please use this shortcode:

[rwmb_meta meta_key="field-id" link="true" size="thumbnail"]

You can also use code snippet, if you don't want to use shortcode:

$images = rwmb_meta( 'field-id', array( 'size' => 'thumbnail' ) );
foreach ( $images as $image ) {
    echo '<a href="', $image['full_url'], '"><img src="', $image['url'], '"></a>';
}

For more info, please check out the docs.